[However, I cannot imagine anyone preferring the current behavior (for a
value of t). Click the mouse or move the cursor and the highlighting
disappears? How could that be desirable?]
It is not obvious to me that this is bad.
Anyway, this option is already implemented, so it takes
essentially no work to keep it as an option.
There is no point eliminating it.
Would someone please try implementing the other behavior
that you've asked for?